Crankshaft tail/spigot bush

[Mark Wilson]

I'm replacing the bronze spigot bush in my 1275 Midget engine as part of my rebuild - purely precautionary as I don't know the history of this engine. The previous one came out very easily using the bread and dowel method , but it had been left protruding from the pocket in the crankshaft by about a third of its length with space behind it.

I'm assuming that this was an unfinished job, and that the replacement bush should be drifted in the full depth of the recess, but can anyone confirm that this is correct?

Thanks

Mark

[philthehill]

Mark
Firstly what engine number prefix do you have as there are two spigot bushes listed for the 1275cc engine.
They are: Pt No: 1A1559.............. early 12CC engines.
Pt No: AHU1026............ late 12CC/12CE & 12V engines.

There is also a needle roller bush listed under Pt No: AHU1026A

What ever bush / roller bearing is fitted the rear bearing face should be level with the rear face of the machined counterbore in the tail of the crankshaft. It should not protrude outside/rearwards of the face of the machined counterbore.

What gearbox do you have fitted as that may give a pointer as to the as found spigot bush fitment/position?
Phil

[Mark Wilson]

Thanks Phil. I don't have the luxury of an engine ID plate, but pretty certain it's a very early CE (thick flange but EN40B crank. Endless debates on the Midget forums, but it does seem that this could have been the original spec, although the crank could have been changed). The bush supplied by Sussex Classic Car Parts is the 1A1559 which fits and looks identical to the one removed - they only offer this and the roller bearing.

I intend to use a Midget 1275 box, subject to what I find when I strip it in a couple of weeks. This was sourced separately from the engine, so no clues there.

By counterbore do you mean the narrowest section, ie what I called the pocket?

[IslipMinor]

Mark,

Definitely do not want to be a prophet of gloom, but it would be worth checking the part number of the primary/input shaft of the 'new' gearbox to make sure that it is the proper close ratio 1275 Midget box.

The table below gives the relevant part numbers:
[frame][/frame]
Hopefully it is 22G229???

[philthehill]

Mark
The thick flange block is the most sought after 1275cc Midget/Sprite engine block and usually commands a premium price when offered for sale.
The EN40B spec crankshaft was the original specification as the original 1275cc Midget/Sprite engine was built to virtually the same specification as the Cooper S but made for an inline installation.
The EN40B crankshaft was Nitrided and if reground more than 0.010" needs to be re-treated.
The original specification conrods were also the same as the Cooper S EN24V - forging numbers AEG177 or AEG521.
The rods were later reduced to EN21 spec but more than adequate for normal use.

A nice set of AEG177 rods currently on 'e' bay
http://www.ebay.co.uk/itm/Set-Original- ... SwHMJYLIOo

The counterbore is the narrowest tube section in the rear of the crankshaft which you call the pocket.

Regarding the gearbox - as Richard says - before you do anything re stripping the box check the Pt Number (22G229) stamped on the first motion shaft just to the rear of the splines.

[Mark Wilson]

Thanks both. I'll fight my way through to the gearbox tomorrow to check, but I vaguely remember the very respectable MG enthusiast who sold it to me last year mentioning the 22G229 first motion shaft ID. It does have the reverse switch in the remote and the tappings for a clutch slave. Hijacking my own thread a bit, it will be my first adventure with gearboxes. I will be using the manual plus Biomed's guide - but unlike most who do this I'm not actually aware of any faults as I've never used it. I intend checking all teeth and bearings, but is there anything other than gaskets which would be false economy not to replace, in the same way you'd never not replace a clutch thrust bearing once you'd stripped that far?

Going back to the engine, yes Phil, it does look to be a good one - and so it should, as you gave me good advice on the flange thickness before I bought it! The conrods are AEG521, but unfortunately the mains are -030 so little benefit from its excellent pedigree. It's only going to be giving my Trav a little extra oomph, not hill climbing, so I haven't gone for heat treatment, just had it checked and polished.

Mark

[IslipMinor]

Mark,

Difficult to tell without having used it, but I would definitely replace the rear oil seal, the layshaft and the 2 layshaft needle roller bearings. If the primary shaft has any sign of 'waggle', I would also replace the primary shaft bearing. Other than that maybe the needle roller bearings on the mainshaft gears, and certainly check the baulk ring synchro cones and hubs for wear.

If you take it off, the mainshaft ball bearing might as well be replaced as a precaution, and as you already have planned, all the gaskets.

[Mark Wilson]

Just checked and definitely 22G229, but with quite a bit of waggle on the input shaft. Lucky I'm enjoying the learning process!

Thanks

Mark

[IslipMinor]

Mark,

'Quite a bit of waggle' = new primary/input shaft bearing! Also replace the spigot needle roller bearing in the end of the primary shaft that takes the end of the mainshaft - 88G409 from the BMC/BL Mechanical Parts List

[philthehill]

Whilst the photo shows the needle roller first motion shaft bearing the orientation in the rear of the crankshaft is the same whether it be a plain bush or needle roller.[frame][/frame]

[Mark Wilson]

Really helpful, thanks - I'd spent quite a long time looking for a photo like that before asking on here!